This application claims the benefit of German Application DE P 19938628.5 filed Aug. 14, 1999, herein incorporated by reference.
The present invention relates to a yarn winding device having a yarn splicing device associated therewith, such as a winding station (sometimes referred to as a winding head) of an automatic bobbin winding machine which is commonly equipped with a splicing device for connecting yarn ends, e.g., after a yarn break. More particularly, the present invention relates to such a winding device having a splicing device wherein a liquid, in particular water, is introduced into the spliced connection.
Splicing devices of the afore-described type typically operate by means of compressed air to connect two or possibly more yarn ends with each other by first opening, i.e., separating and loosening, the individual spun fibers of the yarn ends and then applying one or several spurts of compressed air to the loosened spun fibers of both yarn ends. A relatively strong connection resistant to tensile forces is created by the mutual entanglement, hooking together, swirling and winding of the fibers of the yarn ends. With particularly thin strands, or with strands of a particular fiber structure, the cohesion of the respective fibers to each other may possibly not be sufficient to achieve a splice of a desirable strength. In such cases wherein yarns consisting of particular spun fibers, for example flax fibers, do not have acceptable cohesive characteristics for splicing, a metered amount of a liquid is added to the yarn ends and a so-called wet splice is created to improve the connecting process, the stability and/or the appearance of the spliced location. Besides the yarn from flax fibers, wet splices are also employed with yarn of other natural vegetable fibers, such as cotton thread or denim yarns.
Such a yarn splicing device is known, for example, from German Patent Publication DE 33 37 895 C2, wherein an injection device adds water to the splicing air during splicing. In this device, the amount of water must be exactly metered, atomized and conducted to the splicing chamber together with the similarly metered splicing air.
A preferred case for the employment of splicing devices is, for example, in the winding stations of bobbin winding machines, such as are disclosed in German Patent Publication DE 196 50 879 A1.
In a further embodiment of a wet splicing device, such as represented in German Patent Publication DE 33 23 982 C2, a moistening line terminates in the compressed air line leading to the splicing chamber. By this arrangement, the amount of moisture is meteringly introduced as a function of the length of the compressed air spurt.
The introduction of novel yarn technologies, in particular in the field of compact spinning, considerably increases the requirements made on wet splicing devices in comparison with the requirements made on the connecting techniques of yarns for producing linen.
The degree of general soiling of the winding station by the moisture given off during wet splicing in the course of the winding process plays an increasingly larger role. It is therefore desired to be able to keep the amount of splicing water low. The amount of water can be applied in a metered fashion by means of devices and methods such as described in already mentioned German Patent Publication DE 33 37 895 C2.
However, with every reduction of the amount of splicing water employed, the assurance that the splicing device receives sufficient water for the required stability of the wet splice, and therefore the stability of the yarn, is also reduced. For example, if an amount of water is selected for metering which clearly lies above the customary amount of water required for a sufficient stability of the yarn, then although an obstruction in the introduction of the water, for example by dirt in the feed line, will cause the amount of splicing water to fall below a set value, sufficient moisture will still always be introduced into the spliced connection to achieve the required stability of the yarn. On the other hand, if the predetermined setting of the amount of splicing water to be introduced into the spliced connection were to be reduced so greatly that the moisture in the spliced connection would be just sufficient for generating the required stability, the actually applied amount of water would no longer be sufficient if there were even a slight obstacle in the water supply, which would result in a noticeable lowering of the moisture content of the spliced connection. In turn, the stability of the spliced connection, and therefore the durability of the yarn, would become unsatisfactory in such case and would lead to yarn breaks, potential interruption of or other interference with the course of further yarn processes or uses, or also to reductions in the quality of the finished yarn. To avoid these disadvantages, the size of the amount of moisture to be applied in accordance with the known methods is kept relatively small, but for safety reasons is still made large enough so that it considerably exceeds the amount of moisture required for sufficient stability of the wet splice. Because of the mentioned concerns about the dependability of a wet splicing operation, the available tolerance for lowering the amount of moisture to be applied has not been exhausted or optimized in the known wet splicing devices.
It is accordingly an object of the present invention to provide an improved wet splicing device which addresses the above mentioned disadvantages of known wet splicing devices and will eliminate or at least reduce such disadvantages. In particular, it is an object of the present invention to provide a wet splicing device which will assure a sufficient, moisture-dependent stability of spliced yarn connections while also reducing the amount of moisture to be applied in comparison to that of conventional wet splicing devices.
In accordance with the present invention, this objective is attained in an embodiment of a wet splicing device in a winding station of an automatic bobbin winding machine wherein a capacitive sensor is employed for purposes of evaluating the character and sufficiency of wet yarn splices formed with the device.
In a winding device employing a wet splicing device in association with a downstream yarn cleaner, the use of a capacitive sensor, such as is known, for example, from U.S. Pat. No. 3,106,762, is contraindicated, because even the smallest amounts of moisture from wet splice connections which may be deposited in the area of the capacitive sensor will lead to significant distortions of the yarn cleaning result. The same contraindication applies correspondingly to the employment of combined capacitive/optical sensors, such as are known, for example, from European Patent Publication EP 0 401 600 A2. If a drop of water clings to a sensor, distorted measurements result, and the respective sensor or measuring head can be wrongly adjusted. Subsequently, when the drop dries, a yarn number alarm can occur. This interferes with the production and the monitoring of the yarn quality. Although the amount of moisture may be kept relatively low in a wet splice, the capacitive measured values of the yarn change considerably because of this amount of moisture introduced, and would disadvantageously affect or distort the continuing monitoring of yarn quality. As a result, only optical sensors are customarily employed at winding stations with wet splicing devices. But the employment of only optical sensors considerably limits the measuring abilities and options, and therefore the number of measurable yarn parameters, as well as the dependability of the measured results, are more limited than could be achieved by the simultaneous evaluation of capacitive and optical measured values.
The present invention departs from the conventional wisdom and overcomes the prejudice that capacitive sensors should be avoided in connection with moistened spliced connections, as well as the conventional wisdom and prejudice that the desire for the smallest amount of water unavoidably leads to losses in the assurance of the yarn quality.
In accordance with the present invention, a capacitive sensor is arranged in the winding station downstream of the wet splicing device, by means of which a change in the dielectric value of the moistened spliced connection can be detected. The sensor is connected with an evaluation unit, which generates a signal when a predeterminable threshold value is not reached. Preferably, the generated signal is used as the error signal. An error report can be advantageously generated on a display means. In a preferred embodiment, a yarn cleaner is arranged in the yarn path, and the generated signal triggers a cleaning cut of the yarn. It is possible by means of such an embodiment of the winding station to remove an unsatisfactory spliced connection and to replace it by a proper spliced connection.
Spliced connections which are not moistened, or insufficiently moistened, are assuredly detected in this manner. The amount of splicing liquid which must be supplied and the resulting danger of soiling of components of the winding station may therefore be lowered. The effects on or distortion of measured values, and the continuing monitoring of the yarn quality, because of soiled sensors can be avoided.
Preferably, a memory for storing the generated signals is provided, whereby the generated signals may be used for monitoring the ability of the splicing device to function. In turn, in addition to remedying a lack in quality caused by spliced connections which are not sufficiently moistened, it is possible to also detect and repair a defect in the function of the splicing device. Criteria for the proper functioning of the splicing device and/or the inability of the splicing device to function correctly are preferably predetermined and stored. The generated signals are compared with such criteria and an error signal is generated if deviations from the criteria occur.
Means for cleaning components of the splicing device are advantageously provided. Thus, if an error signal occurs, cleaning of the components, as well as a subsequent repetition of the spliced connection, may be activated. The creation of further defective spliced connections may be prevented by turning off the winding station when an error signal has been issued.
In a preferred embodiment, the dielectric value is only specifically detected in the area of the spliced connection when the spliced connection passes the sensor, and a continuous mass determination of the yarn is not performed. Erroneous evaluations, in particular regarding the mass of the yarn, are avoided in this manner. An optical sensor is preferably also provided in addition to the capacitive sensor. The capacitive sensor advantageously also performs measurements of the yarn outside of the area of the spliced connection.
The determination of the density of the yarn, and therefore of a further yarn parameter, can be performed because of the employment of an optical sensor in addition to the capacitive sensor. With a combination of an optical sensor and a capacitive sensor, one sensor alone can perform the continuous checking of the yarn if the other sensor is temporarily used for other purposes.
As a result, the options for the use of the measuring arrangement, the number of measurable yarn parameters, as well as the dependability of the measurements are considerably increased. Means for determining statistical data regarding the total bobbin quality, as well as a monitoring system for displaying the results, are advantageously used for the further assurance of the yarn quality.
Soiling of the sensors or of the winding station in general by the moisture emitted by the spliced connection can be prevented if the amount of liquid introduced into the spliced connection lies below 0.15 ml, and in particular below 0.1 ml. The threshold value is less than the desired amount. The difference between the desired amount and the threshold value must at least correspond to the amount of water required for a sufficient stability of the spliced connection.
In a simple manner the present invention makes it possible to utilize the advantages resulting from a reduction of the amount of moisture introduced into the spliced connection, and to avoid the disadvantages of too large an amount of moisture in the spliced connection, without endangering the assurance of achieving a sufficient durability of the yarn and a desired yarn quality.
Further details, features and advantages of the present invention will be described and will be understood from the disclosure of a preferred embodiment of the present invention hereinbelow with reference to the accompanying drawing figures.